1. Field of the Invention
The present invention relates to image forming apparatuses, such as copying machines and laser printers, that adopt an intermediate transfer system of an electrophotographic system or an electrostatic recording system for transferring a toner image formed on an image bearing member onto an intermediate transfer member and thereafter transferring the toner image onto a transfer material.
2. Description of the Related Art
A configuration is conventionally known which transfers a toner image from a movable image bearing belt bearing the toner image, to a transfer material in a transfer nip portion.
Japanese Patent Application Laid-Open Nos. 2001-356538 and 2006-330702 disclose image forming apparatuses including a guide member provided upstream of the transfer nip portion in order to guide the conveyance direction of the transfer material until the transfer material reaches the transfer nip portion.
Japanese Patent Application Laid-Open No. 2001-356538 discloses a configuration of the guide member in which the guide member guides the transfer material to the transfer nip portion, brings the leading end of the transfer material into contact, first, with the image bearing belt, and in this state, guides the transfer material to the transfer nip portion. However, in this configuration, the leading end of the transfer material may scrape off the toner image borne on the intermediate transfer belt. For with-margin printing, the leading end of the transfer material enters the transfer nip portion before the leading end of the toner image. Thus, the leading end of the transfer material is unlikely to scrape off the toner image. However, even in the with-margin printing, when the leading end of the transfer material is close to the leading end of the toner image (the marginal portion is small), the leading end of the transfer material may scrape off the toner image if a position where the transfer material comes into contact with the image bearer is displaced.
Moreover, in marginless printing in which the toner image is formed all over the transfer material including the edges thereof, the leading end of the toner image enters the transfer nip portion before the leading end of the transfer material. Thus, the leading end of the transfer material is likely to scrape off the toner image.
Furthermore, Japanese Patent Application Laid-Open No. 2006-330702 discloses a configuration in which the leading end of the transfer material is brought into abutting contact, first, with a secondary transfer roller to guide the transfer material P along the surface of the secondary transfer roller 100 to a pre-transfer nip portion. However, in Japanese Patent Application Laid-Open No. 2006-330702, in the conveyance direction of the transfer material, the secondary transfer roller 100 is arranged upstream of an opposing roller opposite which the secondary transfer roller lies via an image bearing belt. Thus, the image bearing belt is bent immediately before the transfer nip portion formed by the opposing roller and the secondary transfer belt via the image bearing belt. The bent portion may make the conveyance of the transfer material unstable. Furthermore, immediately before the transfer nip portion, the toner image and the transfer material lie opposite each other via a very small gap. Hence, electric discharge may occur at the gap. This electric discharge disadvantageously causes the toner image to be spattered immediately before the transfer nip portion.